1. Field of Invention
The present invention relates generally to methods and apparatus for communicating across a computer network. More particularly, the present invention relates to methods and apparatus for efficiently communicating across a digital subscriber loop (DSL).
2. Description of the Relevant Art
As computer usage becomes increasingly prevalent, the ability to share resources between computers has also increased. Computer systems at many different locations are often linked by a network such that information may be shared between the computer systems, e.g., data may be transferred between the computer systems.
Many different protocols may be used to transfer data between computer systems. By way of example, some protocols include an integrated services digital network (ISDN) and a digital subscriber loop (DSL), which are well known to those skilled in the art. Recently, due to the popularity of the Internet, as the volume of data which is transferred between computer systems increases, the demand for the ability to transfer large volumes of information in relatively short periods of time is growing. Accordingly, DSL technology is constantly being improved to address growing demands.
Subscriber loops, as for example DSLs, are commonly used to enable computers to communicate over a network. FIG. 1 is a diagrammatic representation of different subscriber loops in communication with a wide area network (WAN) in accordance with prior art. WAN 104 is essentially the network over which various entities 108a-d are allowed to communicate in order to transfer data. Entities 108a-d may generally include small customers, which are often "residences," e.g., residence customer 108a, that have computer systems and/or entertainment systems that are linked to WAN 104. Entities 108a-d may also include large customers or "businesses," e.g., business customer 108c, which have computer systems that are in communication with WAN 104.
Business customer 108c may often require bi-directional high speed data transfer. By way of example, business customer 108c may need to readily access and update databases located in WAN 104. As such, business customer 108c is typically linked to WAN 104 using data lines which are capable of supporting bi-directional high speed data transfer. A T1 line 112 may be used to link business customer 108c to a node 116 within WAN 104. T1 line 112 has a data transfer rate of up to approximately 1.544 megabits-per-second (Mbps), and uses a single wire to bi-directionally transfer data.
As shown, a high speed DSL (HDSL) line 120 may be used to link business customer 108c to a node 124 within WAN 104. HDSL line 120, like T1 line 112, has a data transfer rate of up to approximately 1.544 Mbps. However, for reliability purposes, HDSL line 120 includes two bi-directional lines which transfer data between node 124 and business customer 108c.
Another type of communications link, an integrated DSL (IDSL), is created when ISDN technologies are applied to DSL. An IDSL line is capable of bi-directionally transferring data at rates of up to approximately 128 Kbps, which is typically sufficient for transmitting voice information between touch-tone (TT) phones. A first IDSL line 136 may be used to connect a TT phone associated with an entity, e.g., residence customer 108b, across WAN 104, to a TT phone associated with another entity, e.g., residence customer 108d, which is connected to a second IDSL line 140. When voice data is to be transmitted from residence customer 108b to residence customer 108d, the voice data is transmitted in analog form across IDSL line 136, which is a copper wire, to a node 144 where the voice data is digitized. The digitized voice data is then routed over WAN to another node 146, where the digitized voice data is converted back into analog form, and sent over IDSL line 140 to residence customer 108d.
Residence customer 108a, unlike business customer 108c, may not require bi-directional high speed data transfer, due to that fact that residence customer 108a is typically more likely to download information, e.g., video data for video-on-demand technologies, through WAN 104 than to upload information through WAN 104. Accordingly, residence customer 108a generally uses an asymmetric DSL (ADSL) connection 128 which includes a "downloading" line that is arranged transfer data downloaded from a node 132, or a central office port, to residence customer 108a at rates of up to approximately 8 Mbps. ADSL connection 128 also includes an "uploading" line which is arranged to transfer data uploaded from residence customer 108a to node 132 at rates of up to approximately 384 kilobytes-per-second (Kbps).
In general, an IDSL connection is considered to be sufficient to transfer voice data between TT phones because the volume of data transfer is relatively low. However, in order to transfer data relating to the Internet, e.g., World Wide Web pages and video-on-demand data, to Internet customers such as residence customers, an ADSL connection is typically preferred over an IDSL connection. Internet usage typically involves downloading information to a computer system, as for example a computer system associated with the residence customer. Hence, since an ADSL connection is arranged to provide the capability to quickly download relatively high volumes of data to a computer system, while still enabling data to be uploaded from the computer system when necessary, an ADSL connection is particularly suitable for use by customers who generally download data.
Although an ADSL connection is effective for use in transferring data over the Internet, an ADSL connection typically requires a dedicated node, e.g., a dedicated central office port with an ADSL card, as well as dedicated power for each Internet customer. FIG. 2 is a diagrammatic representation of conventional point-to-point ADSL connections to a central office (CO). As shown, a system with point-to-point ADSL connections 202 includes customers 204a-l, e.g., residences, which are each linked to a central office 206 via ADSL connections 210a-l. Specifically, customers 204a-l are linked via ADSL connections 210a-l to dedicated ports 214a-l associated with central office 206.
Each customer 204a-l generally has a point-to-point ADSL card which is connected to an appropriate ADSL connection 210a-l. The appropriate ADSL connection 210a-l is connected to a point-to-point ADSL card at central office 206 (not shown) which is associated with an appropriate port 214a-l. ADSL cards include point-to-point ADSL cards, such as those which are available commercially from Interphase Corporation of Dallas, Texas.
An ADSL connection, as for example ADSL connection 210a is generally comprised of a copper twisted pair over which data is transmitted downstream to customer 204a, and upstream from customer 204a to central office 206. Due to the fact that availability of copper wire is relatively fixed in the current communications network infrastructure, and, further, that separate ports, such as port 214a, are required for each customer 204a-l, the implementation of point-to-point ADSL is often expensive.
Since data transferred over the Internet is bursty data, as will be appreciated by those skilled in the art, ADSL connections, e.g., ADSL connections 210a-l, are not active, or in use, much of the time. Therefore, as the full bandwidth associated with the ADSL connections is largely unused, resources associated with the ADSL connections are often essentially wasted. Further, as the length of an ADSL connection increases, the effective data transfer rate decreases. In other words, as the distances between a central office and an Internet customer increases, the data transfer rate across an ADSL connection between the central office and the customer decreases. As a result, while ADSL connections may transfer data at rates of between approximately 6 Mbps to approximately 8 Mbps, due to noise and attenuation which increase as the distance from a central office increases, many ADSL connections transfer data at substantially lower rates, as for example at approximately 384 Kbps. For example, with reference to FIG. 2, the maximum data transfer rate associated with ADSL connection 210f, which is relatively close to central office 206, may be approximately 6 Mbps to approximately 8 Mbps, while the maximum data transfer rate associated with ADSL connection 210a, which is relatively far removed from central office 206, may be approximately 384 Kbps.
Since the costs associated with an ADSL connection are generally high, as mentioned above, when an ADSL connection is only able to download data at rates of up to approximately 384 Kbps due to the length of the ADSL connection, the use of the ADSL connection may be considered to be inefficient. In addition, allowing an ADSL connection to a central office to remain idle while awaiting the transmission of data characterized as bursty data is an inefficient use of ADSL technology, as well as central office, resources.
Therefore, what is desired is an efficient method for utilizing DSL connections and central office resources, while maintaining an acceptable data transfer rate over the DSL connections, especially ADSL connections.